SATURDAY, April 10 (HealthDay News) -- Because their brains process the world around them in a different way, introverted or shy people respond differently to physical and emotional stimuli than other people, according to a new study.

About 20% of people are "highly sensitive," an inborn trait that can be seen in children who are reserved, need little disciplining, cry easily, ask unusual questions or have especially deep thoughts, explained Elaine and Arthur Aron and colleagues from Stony Brook University in New York and in China.

Adults who are highly sensitive tend to take longer to make decisions, are more conscientious, spend more time alone to reflect and are more easily bored by small talk, the study authors noted.

The researchers used functional MRI to scan the brains of sensitive and non-sensitive people as they tried to identify small changes in photographs. The changes that the study participants tried to identify were either obvious or subtle.

Compared to non-sensitive people, the sensitive participants looked at the photos that had the subtle changes for a longer time and had much greater activation in brain areas involved in associating visual input with other input to the brain, and with visual attention. These areas aren't used simply for vision, but for a deeper processing of input.

The findings were recently published online in the journal Social Cognitive and Affective Neuroscience.